Conodont zonation of Lower Triassic strata in Slovenia

The paper presents the results of a conodont study carried out in the Triassic strata in the area of the Slovenian part of the Southern Alps, External Dinarides and the Transition region between the External and Internal Dinarides. The following conodont zones have been distinguished: Hindeodus praeparvus Z., H. parvus Z., Isarcicella lobata Z., I. staeschei – I. isarcica Z., H. postparvus Z., Hadrodontina aequabilis Z., Ha. anceps Z., Eurygnathodus costatus Z., Neospathodus planus Z., N. robustus Z., Platyvillosus corniger Z., Pl. regularis Z., Pachycladina obliqua Z., Foliella gardenae Z., Triassospathodus hungaricus Z., T. symmetricus Z., N. robustispinus T. homeri Z. and T. triangularis Z. The introduced conodont zonation spans from the Induan, including the Permian-Triassic boundary interval to the late Olenekian and is valid for the shallow shelf environments of western Tethys.


Introduction
Conodont research in Slovenia started back in the sixties of the last century, during the time of elaboration of the Basic Geologic Map of Yugoslavia 1 : 100,000. The first analysis of conodont samples were carried out by the Serbian paleontologist Smiljka Pantić who determined the fauna from Lower Triassic strata of the Polhograjsko hribovje Hills (Grad & Ferjančič, 1976). Despite a rapid development of Slovenian conodontology in the following period, Lower Triassic strata were considered for more than two decades being poorly perspective for conodonts. It was only in the eighties of the last century when the fauna of the Smithian Parachirognathus / Furnishius conodont zone was collected in a section near Idrija (Kolar-jurKovšeK, 1990). In the following decades an intensive conodont research of the lowermost Lower Triassic succession contributed to definition of the Permian-Triassic boundary (PTB) interval, first in Slovenia, and then in the broader area of the Dinarides of Croatia and Serbia (Kolar-jurKovšeK et al. 2011c, 2012aljinović et al., 2014;Sudar, 2007).
After the Permian-Triassic catastrophe, as often named the greatest mass extinction, the global biosphere was greatly impoverished and needed some time to be able to recover to the previous diversity, as at the end of the Permian 70 % of genera of terrestrial vertebrates and 85 to 96 % of marine invertebrate species that lived at the end of the Paleozoic became extinct (Benton, 2005). The first pulse of extinction was already between the Middle and Upper Permian, at about 260 million years ago and the second between the Permian and Triassic, at about 252 million years ago. For the second -the main pulse between the Permian and Triassic a pronounced increase in volcanic activity was especially fatal. In the PTB interval sedimentary rocks is documented a sudden drop in δC 13 that is today by researchers mostly linked with the release of frozen gas hydrates on the seafloor (Berner, 2002). The climate changes caused a change in ocean currents and change of the pH of sea water that greatly increased aridity in the supercontinent inland. Some studies indicate long-term global deep anoxic event in the PTB interval. The Panthalassa Ocean became fully stratified for almost 20 million years. Beginning, peak and the end of the oceanic stratification corresponds to the global biotic events from the decline in the number of species at the end of the Guadalupian, and extinction at the end of the Permian to the full recovery of life during the Anisian (iSozaKi, 1997(iSozaKi, , 2009). Due to coincidence of timing of different triggers of the Permian-Triassic extinction, the biodiversity in the Mesozoic was significantly reduced for entire 25 million years.
In general, the Triassic Earth's crust was relatively stable until the Late Triassic, when disintegration was intensified caused by continental rifting. The Tethys Ocean, which has already begun to develop in the Permian south of the Paleotethys or south of the lands of Cimmeria, started to incise increasingly to the west during the Triassic and later already in the Jurassic it divided the Pangea into two halves, on Gondwana and Laurasia.

General geological setting
Slovenia is situated in the area of four major geotectonic units: the Dinarides, the Southern Alps, the Eastern Alps and the Pannonian Basin. Today's geological image of Slovenia is largely result of the collision of the Adriatic and European plates and accompanying tectonic processes, which persist even today. Paleozoic and Mesozoic structures are thus largely deformed, blurred or covered with sediments of the Pannonian Basin. All tectonic units of the Slovenian territory belong to the Adriatic lithosphere plate, which was originally connected to the African plate, and from the Mesozoic era onwards existed as a separate plate.
Paleozoic rocks of today's Slovenia were formed in the northern part of the former southern supercontinent Gondwana, mainly on its epicontinental shelf. More clearly their origin is  recognized in the late Paleozoic, when most of the Earth's land masses were united in a supercontinent Pangea. From the east the Paleotethys Ocean incised in it, and at its southern end, however, the Tethys Ocean began to open (Fig. 1). Then an intensive intraoceanic carbonate platform gradually began to form in an autonomous Adriatic lithosphere plate. During the Permian and Lower Triassic there was still a unified sedimentation area, and its smaller part in Slovenia is called the Slovenian Carbonate Platform (BuSer, 1989). During the Anisian and Ladinian the Slovenian Carbonate Platform began to disintegrate as a result of extensional tectonics on the edge of Eurasia, where the Meliata Ocean began to originate (Vrabec et al., 2009). All the activities were accompanied by strong volcanism. Until that time a uniform Slovenian Carbonate Platform disintegrated in the Adriatic-Dinaric Carbonate Platform in the south, and the Julian Carbonate Platform in the north, with an intermediate Slovenian Basin (BuSer, 1989;BuSer et al., 2007BuSer et al., , 2008. In today's geotectonic structure of Slovenia (Placer, 1999;PoljaK, 2000) to the Southern Alps belong the sedimentary rocks that built large part of the Southern Karavanke, Julian Alps and the Kamnik-Savinja Alps. To the Transitional area between the External and Internal Dinarides belongs the area which extends from central Slovenia across the Sava Folds to the east and south-east to the Dolenjska and Gorjanci regions and continue further to Croatia. To the External Dinarides corresponds a greater part of southern and south-western Slovenia. To the Eastern Alps in Slovenia is ranked a territory of the Northern Karavanke situated north of the Periadriatic Lineament (Fig. 2).

Overview of the Early Triassic sections with conodonts
Lower Triassic marine sedimentary rocks in the area of the Southern and Eastern Alps, the External Dinarides and the Transitional area between the External and Internal Dinarides were sampled for conodont research. In all units the lithostratigraphic development of the Lower Triassic strata is more or less similar. Their lowest part containing conodonts of the PTB interval gave positive results only in the Idrija-Žiri area belonging to the External Dinarides. In the other units Olenekian conodonts were identified, whereas the conodont research of Lower Triassic strata in the Slovenian part of the Eastern Alps were negative.
Base of the Lower Triassic strata in all these geotectonic units is formed of limestone and dolomite of the Bellerophon Formation as a result of general marine transgression in a shallow shelf of west Paleotethys in the Late Pemian. For convenience, it is necessary to clarify the names of the Late Permian lithostratigraphic units, that were used in Slovenia. The first is the Karavanke Formation of the Southern Alps (BuSer et al., 1989), which is represented mainly by dolomite development, and in its upper part there occur limestone and dolomite with characteristic Late Permian fossil association of the Bellerophon Formation (SKaBerne et al., 2009). The second is the Žažar Formation of the External Dinarides, which was named by ramovš (1958 a, b) and he distinguished twelve limestone levels with a brachiopod fauna of the Caucasus-Indoarmenian type. The name of the Žažar Formation was later taken up by some researchers (Grad & Ferjančič, 1976;BuSer et al., 1989;dolenec et al., 2004;mlaKar & čar, 2009), although it is the lithological and biostratigraphic equivalent of the Bellerophon Formation of the Carnic Alps and the Dolomites in Austria and Italy (FaraBeGolli et al., 1986;HolSer & ScHönlauB, 1991).
Following a decision of the International Commission of the IUGS (Yin et al., 2001) to define the PTB based on the first appearance datum (FAD) of a globally spread conodont species Hindeodus parvus (Kozur & PjataKova), there was also in Slovenia greatly increased interest to study the PTB interval. Researchers were particularly interested in the Idrija Žiri area in the western Alpine foothills. The geological structure of the area is relatively well known due to elaboration of the Basic Geological Map SFRY 1: 100,000, sheet Tolmin and Udine (BuSer, 1986(BuSer, , 1987 and also due to extensive geological research of the Idrija mercury mine area (mlaKar, 1969;Placer, 1973Placer, , 1981mlaKar & čar, 2009;čar, 2010). In sections in which the PTB is located entirely in the dolomiteevaporite strata, paleontological research did not reveal any results. However, in the sections in a limestone development, the boundary was often placed on the upper lithological boundary of the Bellerophon Formation (Grad & oGorelec, 1980;BuSer et al., 1989;mlaKar & Placer, 2000;mlaKar & čar, 2009;čar, 2010). There are two particularly interesting well-exposed sections in the limestone development near Idrija town (Masore and Idrijca sections), in which the PTB was defined on the basis of geochemical -isotopic studies (dolenec & ramovš, 1998;dolenec & oGorelec, 2001;dolenec et al., 1999a, 1999, 2004. The goal of an ongoing study of the two sections is to define the PTB based on biostratigraphic evidence.
In the Lukač section near Žiri in the External Dinarides, the PTB was for the first time defined in Slovenia according to an international criterion based on the finding of the conodont species H. parvus . The section is similar to most other studied Permian-Lower Triassic sections in the Idrija-Žiri area of the Trnovo nappe, which is the highest thrust unit of the External Dinarides in this area. The obtained conodont faunas of the Lukač section enabled very fine biozonation due to rapid evolution of the genera Hindeodus and Isarcicella and for this reason the Lukač section represents a key section to define PTB interval strata in Slovenia that is taken also as a standard for conodont zonation for the whole Dinaric area (Kolar-jurKovšeK et al., 2011a, 2011b, 2012 -jurKovšeK et al., 2006-jurKovšeK et al., , 2011a. Late Permian-Early Triassic succession of the Lukač section continues to the northwest and in a similar form it is exposed in a road cut of the Javorjev Dol area. Grad and oGorelec (1980) set the the PTB in a dolomite, which corresponds to the Evaporite-dolomite Member of the Bellerophon Formation. Conodont fauna collected in the limestone of the Bellerophon Formation below the dolomite yields H. praeparvus Kozur and H. latidentatus (Kozur, Mostler & Rahimi-Yazd). However, the actual boundary with the Lower Triassic strata that outcrop along the road about 30 m in a direction to Sovodenj is covered and tectonized. In the Lower Triassic oolitic limestone strata I. isarcica (Huckriede) was collected.
In the Idrija-Žiri area three sections with the PTB are currently studied: the Masore, Idrijca and Vojsko sections. Conodont faunas were recovered from all three sections.
In the Masore section the limestone of the Bellerophon Formation attains a thickness of about 250 m. Its upper part is characterized by the fauna of the H. praeparvus Zone that has relatively wide range. The Bellerophon Limestone passes then through thin bedded, predominately microbialite limestone with stylolites into the Lower Triassic bedded limestone containing typical Induan conodont association with I. isarcica.
The same strata of the Permian-Triassic boundary as in the Masore section, occur 2 km laterally in the valley of the river Idrijca. There is visible only the highest part of the limestone of the Bellerophon Formation and the lowest microbialite part of the Lower Triassic strata . Also here were identified conodonts of the H. praeparvus Zone in the highest part of the Permian portion of the section, and the I. isarcica -I. staeschei Zone in the Lower Triassic microbialite part of the section.
The Vojsko section is situated on the eastern slope of the Vojsko plateau at an altitude of 770 m. According to Placer (1981) it belongs to the Kanomlja thrust slice, which lies directly below the Trnovo nappe, and the rocks are in the inverse position. Unlike the Masore section, where over 250 m thick succession of the Bellerophon Formation is exposed, in the section Vojsko only around 30 m of thickness is visible (mlaKar & čar, 2009;čar, 2010). In the highest part of the formation, about 2 m below the lithological boundary with light gray stromatolitic dolomite, there occur very rare and small sponge buildups (Sremac et al., submitted). The conodont fauna of this part is assigned to the H. praeparvus Zone.
Above the Bellerophon Formation lies medium gray thin bedded stromatolitic dolomite with clear lamination and stylolites that passes up to the medium bedded and slightly recrystallized dolomite and dolomitized limestone in which a conodont fauna of the I. staeschei -I. isarcica Zone was found. In the stratigraphically younger parts an increased content of limestone and clastic components is observed, initially in the form of olive green marl, then reddish brown calcarenite, siltstone and shale with lenses of oolitic limestone, followed by more than 100 m grained dolomite. The Lower Triassic sequence is ended by bedded dark gray limestone containing marl sheets, above which concordantly lies Anisian dolomite (čar, 2010).
In addition to the study in a context of the previously described sections Lukač, Masore, Idrijca and Vojsko that include the PTB interval, interesting results of conodont study were obtained also in some other Lower Triassic sections in the Idrija-Žiri area. It should be noted that the names of most Lower Triassic lithostratigraphic units in the External Dinarides have been traditionally based on the subdivision in the Dolomites and the Northern Calcareous Alps. Therefore also Slovenian geologists often divided the so-called Werfen Formation into lower »Seis Beds« (Seiser Schichten) and the upper »Campil Beds« (Campiler Schichten). Biostratigraphy of Lower Triassic strata was based mainly on macrofossills: ammonites, bivalves and gastropods, rarely on foraminifers, but conodont study was implemented only in a recent two decades. Precise litho-, bio-and chemostratigraphic study have demonstrated the lateral and vertical differences and similarities in litho-and biofacies of adjacent areas. Therefore, the »Seis« and »Campil« beds in the Slovenian part of the External Dinarides can no longer be regarded as chronostratigraphic equivalent of the facies of the Southern Alps (aljinović et al., 2013 a, b). Distribution of Lower Triassic sediments in the External Dinarides clearly demonstrates temporal and lateral change of carbonate and siliciclastic sediments depending on various transgression-regression cycles on the extensive epeiric carbonate platform of west Tethys. Despite lithological variations between different Lower Triassic sedimentary areas in the External Dinarides in almost all sections their threefold division can be recognized into: the oldest part consisting of carbonates, the middle siliciclastic or mixed siliciclastic-carbonate part, and the third or the highest carbonate part (BuSer 1969(BuSer , 1974aaljinović et al., 2013a, b).
Already the first conodont study of the Lower Triassic strata of the Idrija-Žiri area in the nineties of the last century demonstrated that the greater part of the reddish »Seis« shales, siltstones and sandstones that contain also layers of oolitic limestone are not of the Induan but Olenekian in age. In the Želin-Vrlejca section a characteristic Smithian fauna with the following taxa: Furnishius triserratus Clark, Hadrodontina sp., Pachycladina obliqua Staesche and Parachirognathus ethingtoni Clark was documented and ranged to the Parachirognathus/ Furnishius Zone (Kolar-jurKovšeK, 1990). The greater part of the Lower Triassic represented an extended recovery event following the Permian-Triassic mass extinction, as well as being marked by three minor crises (StanleY, 2009), which were reflected particularly in ammonites and conodonts during the late Griesbachian, late Smithian and late Spathian. The Smithian-Spathian boundary is indicated by a global warming (GalFetti et al., 2007;Sun et al., 2012), which is also indicated by a positive shift of δ 13 C carb (ricHoz, 2006) as well as conodont size reduction .
A systematic sampling of five Lower Triassic sections in the Idrija-Žiri area of the Trnovo nappe has yielded the best Early Triassic conodont sequence in central and southern Europe. The recovered conodont faunas enabled us to distinguish nine conodont biozones spaning from the late Induan (Dienerian) to the Olenekian (Spathian) (cHen et al., 2015 a). In the five studied sections following conodont zones were determined: Eurygnathodus costatus Z., Eurygnathodus hamadai Z., Foliella gardenae-Pachycladina obliqua A.Z., Neospathodus robustus Z., Platyvillosus corniger Z., Platyvillosus regularis Z., Triassospathodus hungaricus Z., Triassospathodus symmetricus Z., and Neospathodus robustispinus Zones. The succession of the Lower Triassic zones is of particular value for stratigraphic correlation in central and southern Europe and it enables better correlation studies between the western and middle-eastern Tethys.
The sections in vicinity of Spodnja Idrija and Žiri could be regarding their position above the »Seis« beds traditionally compared with the »Campil« beds of the Dolomites, that in the highest part often contain Olenekian fauna with the ammonites of the genera Tirolites and Dinarites, gastropods Natiria and Turbo and foraminifera Meandrospira pusilla (Ho). Since the development of Olenekian strata of the Žiri area significantly differs from the typical Campil Beds, the local beds are ranged to the new informal lithostratigraphical unit, the "Žiri Beds" .
In the western part of the Alpine foothills the conodont study was directed to the Polhograjsko hribovje hills, which are situated west of Ljubljana between the Ljubljana moor in the south, Podlipščica to the west and to the north it is separated from the Škofja Loka hills by the Poljanska Sora River. All studies from different sections and outcrops have confirmed only the Olenekian age, whereas Induan strata have not been identified in this area.
In the Tehovec section, southwest of Medvode, a slightly marly biomicrite limestone lies on a thick bedded dark gray dolomite and with thin marlstone intercalations. In several beds also oolites are encountered. Among fossil molluscs there are represented Natiria costata (Münster) and Costatoria costata (Zenker) as well as rare badly preserved ammonites. Among the microfossils in the greater part of a 47 m section foraminifera M. pusilla occurs and the conodonts are represented by typical Lower Triassic shallow water elements P. obliqua and genera Hadrodontina and Ellisonia (jurKovšeK et al., 1999). Similar Lower Triassic successions are known from many other localities in the Polhograjsko hribovje Hills (Grad & oGorelec, 1980;ramovš, 1958b). These strata produced conodonts in the Horjul surroundings (Koreno, Samotorca, Prevalc and Šentjošt).
In the External Dinarides, Lower Triassic strata with conodonts were also found in several places of Notranjska and Dolenjska regions. Detail investigations have been done in the sections on the southern and eastern outskirts of the Krimsko-mokrško hribovje hills. BuSer (1969,1974) roughly divided Early Triassic strata into three superposition packages. Below is bedded gray dolomite with claystone and siltstone intercallations, in the middle part is reddish shale and sandstone with intercalations of oolitic limestone, and in the upper part there is light gray dolomite with marl beds. In all sections conodonts were recovered only from the samples of the middle superposition package. The carbonate beds (sparitic limestone, calcarenite and oolite limestone), which are deposited between the reddish claystones, siltstones and fine grained sandstone in the Iška River gorge yield conodonts Ellisonia sp., Foliella gardenae (Staesche) Hadrodontina sp., P. obliqua and P. ethingtoni. The fauna is dominated by the elements of the conodont apparatus P. obliqua at different ontogenetic stages (Kolar-Jurkovšek & Jurkovšek, 1996). Similar conodont fauna was also found in Lower Triassic strata at Draga near Ig (Kolar-jurKovšeK & jurKovšeK, 1996), Četež near Turjak and Borštnik. The recovered conodont elements of these localities are comparable with the obtained Smithian faunas from the Želin-Vrlejca sections of the Idrija-Žiri area and near Tržič (Kolar-jurKovšeK, 1990, Kolar-jurKovšeK & jurKovšeK, 1995. From the middle superposition package of a variegated clastites containing oolitic limestone beds at Skopačnik near Želimlje (dozet & Kolar-jurKovšeK, 2007) a Smithian species F. gardenae and P. obliqua are determined, whereas in the overlying dolomite strata which correspond to the upper carbonate superposition package the Spathian elements T. homeri (Bender) and T. ex gr. triangularis (Bender) were determined.

Similar
lithological developments of Lower Triassic strata with conodonts as in the External Dinarides are also represented in the Transitional area between the External and Internal Dinarides, which extend from central Slovenia to the east on the territory of Croatia. The greater part of the Transitional area belongs to the Sava Folds, where in all of the investigated Lower Triassic strata conodonts were collected only in the middle mixed siliciclastic-carbonate part, which includes also oolitic limestone beds. Northwest of Trojane in the limestone between the reddish and olive grey clastites conodont species Hadrodontina anceps Staesche and P. obliqua have been found, in the Grmače section south of Litija P. obliqua, at Leskovica south of Bogenšperk and along the road between Bogenšperk and Temnica P. obliqua and F. gardenae. In the eastern Kozjansko region in the valley Mišnica north of Jurklošter the species P. obliqua was collected. All reported conodont elements indicate to a Smithian age of the sampled strata. A poorly preserved Early Triassic conodonts of the genera Hadrodontina and Pachycladina and some other non-identifiable fragments yield also some other test samples from the Sava Folds (Dobovica south of Podkum, Čebine north of Zagorje, etc.).
To the Transition region between the External and Internal Dinarides belongs also the Dolinski potok near Mokrice, which is located in the easternmost part of the Gorjanci -Žumberak Mt. near the Slovenian-Croatian border and it includes sedimentary rocks of the Smithian-Spathian interval (Kolar-Jurkovšek et al., submitted). The investigated part of the section is dominated by a thin bedded limestone with marl intercalations. Two limestone lithothypes are mainly represented: biomicrite/packstone and micritic limestone (mudstone). The following conodont zones have been distinguished: Ha. aequabilis Zone, Platyvillosus corniger Zone, Pl. regularis Zone and Triassospathodus hungaricus Zone. The same conodont zones were also discriminated in Lower Triassic sections of the Idrija-Žiri area (Kolar-jurKovšeK et al., 2015b;cHen et al., 2015 a) and they are particularly relevant for correlation of the equvalent strata of the adjacent as well as broader areas with significant sections of Asia and North America. The conodont material from this section has enabled the reconstruction of two conodont multielements: T. hungaricus (Kozur & Mostler) and Pl. regularis (Budurov & Pantić).
The conodont research in the Lower Triassic of the Slovenian part of the Southern Alps was carried out in the eastern part of the Julian Alps, the Southern Karavanke and Kamnik-Savinja Alps. For the Julian Alps, which comprise a large part of north-western Slovenia, is characterized by an overthrust structure. The largest is the Julian nappe (Placer, 2008) or the Julian Alps overthrust (jurKovšeK, 1987 a, b) which is formed of strata ranging from the Lower Triassic through the Cretaceous; its greater part is presented by the Upper Triassic shallow marine carbonates. Lower Triassic strata most frequently occur in discrete narrow bands or within smaller tectonic slices. Their footwall in this part of the Julian Alps is not visible, and in some places they are concordantly overlain by Anisian carbonate rocks.
At Studorski preval (Studor Pass), situated 4.5 km southeast of the peak of Mount Triglav (2864 m), the Lower Triassic strata are predominantly tectonized. In a tectonically undisturbed parts of the section microfacially two basic types occur: coarse tempestite sediment (microfacies A) and laminated or bioturbated calcareous mudstone and / or marl (microfacies B), pointing to a more distal parts of the ramp with storm influence. A similar formation also applies to the depositional environment of the Werfen Formation of the Southern Alps (Brandner et al., 2012). The Lower Triassic strata of Studorski preval are characterized by common gastropods Natiria costata, bivalves of the genera Bakevellia, Avichlamys and Eumorphotis, foraminifer fauna with the genera Ammodiscus, Hoyenella and Glomospirella corresponding the global »Glomospira-Glomospirella« foraminifer association. Ammonites in the microfacies B show that a connection to the open sea was unimpeded. The conodont fauna with T. hungaricus is typical of the lower Spathian . From Lower Triassic strata of the Studorski preval the first discovery of a fossil amphibian in Slovenia (Temnospondyl) was found, which most probably belongs to the group Capitosauridae (lucaS et al., 2008).
Similar Lower Triassic strata with gastropods Natiria costata, bivalves and very rare ammonites are tectonically squeezed in the area of Špica v Sedlcih located about 2 km northeast of the Vršič pass (jurKovšeK, 1987 a, b). In the limestone that corresponds to the microfacies B of Studorski preval some unidentifiable fragments of conodonts were found.
In a wider area of the Southern Karavanke on the dolomite of the Late Permian Bellerophon Formation there rest Lower Triassic strata that pass upward to the Anisian dolomite (BuSer, 1980;BuSer & cajHen, 1978). Lower Triassic strata in the valley Tržiška Bistrica near Tržič belong to the South Karavanke overthrust that is in the south limited with the Sava fault, and in the north by the Košuta overthrust of the Southern Karavanke. The lower and upper boundaries of the investigated sequences are not exposed, but the strata can be roughly divided into two parts (dolenec et al, 1981). For the lower part of the sequence are characterized numerous strata and lenses of reddish oolitic limestone that are interbedded with the shale sheets and limestone beds with detritic admixture. In the upper part there is interbedded darker limestone, sandstone, marlstone and dolomite. A total thickness of the Lower Triassic strata in the section is about 200 m, of which the two parts of the section of approximately the same thickness. Conodonts were collected in the oolitic and sparitic limestone of the lower part of the section (Kolar-jurKovšeK & jurKovšeK, 1995). The recovered conodonts F. gardenae, Ha. anceps, P. obliqua and Pa. ethingtoni suggest a Smithian age.
Lower Triassic strata of the South Karavanke overthrust built a great part of the Kamnik-Savinja Alps in the upper part of Savinja valley. In the area between the Logarska dolina, Solčava, Robanov kot and the northern slopes of Raduha these strata attain thickness up to 1000 m (mioč, 1983;mioč & Žnidarčič, 1983;celarc, 2002, 2004ŽaloHar & celarc, 2010), but due to folding their thickness is only apparant. In the lowest part of the Lower Triassic strata there rests dolomite, which passes upwards into a carbonate-clastic succession of marlstone, siltstones, sandstone and marly limestone. Preliminary sampling of the limestones in the upper part of the stratigraphic sequences at several localities confirmed the presence of the Smithian conodont taxa P. obliqua and Parachirognathus sp., and the Spathian species T. hungaricus.

Conodont zonation
Altogether seventeen conodont zones can be distinguished in Lower Triassic strata of Slovenia (Fig. 3, 4). In this section these zones are described in ascending order, and in the beginning also a description of the latest Permian conodont Zone is added.

Hindeodus praeparvus Zone
(latest Changhsingian) Lower limit: defined by the first occurrence (FO) of Hindeodus praeparvus Kozur (Perri & FaraBeGoli, 2003). Very rare elements of Isarcicella with a widely opened and thickened basal cavity are also present, of which some specimens are designated to Isarcicella cf. prisca Kozur, in the uppermost strata of the Bellerophon Formation. According to Perri (Perri & FarBeGoli, 2003) the genus Isarcicella made its first appearance in the latest Permian and is marker to distinguish the Upper from the Lower H. praeparvus Zone in the Southern Alps. Thus the presence of isarcicellids in the upper part of the H. praeparvus Zone in the Masore section enables to divide this zone in the lower and upper part.

Conodont zonation of Lower Triassic strata in Slovenia
Occurence: Lukač (early Griesbachian; Transitional Beds of the Lukač Formation).
Remarks: I. lobata first appears in the Transitional Beds of the Lukač Formation. This zone is marked by the entry of several other taxa and it represents a recovery event. The entire stratigraphic range of the species H. erectus lies within this zone. Three other taxa (H. postparvus, I. turgida, I. inflata) have their entry (FAD) in this zone, whereas H. cf. eurypyge appears only in this zone.
Remarks: This zone is marked by the entire stratigraphic range and co-occurrence of I. staeschei and I. isarcica. Five taxa (H. postparvus, I. turgida, I. lobata, I. inflata, and Isarcicella sp.) that appeared already in the previous zone continue with their presence in this zone. All associated taxa have the LAD within this zone, except H. postparvus. For the presence of numerous taxa the fauna of this zone is still part of the recovery event.
In the Lukač section the LAD of I. staeschei and I. isarcica coincides with the first occurrence of the genus Hadrodontina of which some elements can be identified as Ha. ex gr. aequabilis. In the Dolomites a successive appearance of some isarcicellid taxa is documented, i.e. I. lobata -I. staeschei -I. isarcica and moreover, the species Ha. aequabilis has a synchronous entry together with I. staeschei.
Remarks: Ha. aequabilis was first described from the Dolomites (StaeScHe, 1964) and its multielement reconstruction was provided by Perri (1991). In the Mokrice section the Ha. aequabilis Zone has been distinguished where the marker taxon is present as a single species (Kolar-jurKovšeK et al., submitted). In the Dolomites, the I. isarcica Zone is succeeded by the succession of the zones based on euryhaline shallow water species: Ha. aequabilis Zone (latest Griesbachian -Dienerian), Ha. anceps Zone and P. obliqua Zone (Perri, 1991;FarBeGoli & Perri, 2012).
Based on comparison with the Dolomites and regarding long range of Ha. aequabilis it is reasonable to conclude that the stratigraphic range of H. postparvus overlaps with the lower portion of the stratigraphic range of Ha. aequabilis. The later species has been reported also from Japan (iGo, 1996) and South Primorye in Russian Far East (BondarenKo et al., 2015).
Occurrence: Lukač (Dienerian; middle and upper part of the Carbonate-clastic Member of the Lukač Formation).
Remarks: Ha. anceps was first described from the Dolomites (StaeScHe, 1964). The Ha. anceps multielement was first reconstructed by Perri & andraGHetti (1987). This zone is well correlated with the Ha. anceps Zone of the Dolomites where it is based on the position between the Ha. aequabilis Zone and followed by P. obliqua Zone (Perri,1991).
Remarks: E. costatus has been first described from the Dolomites, Italy (StaeScHe, 1964). In the Dinaric area and it has been later reported to occur in western Serbia (Budurov & Pantić, 1973), Croatia (aljinović et al., 2006) and in Bosnia and Herzegovina. The species has been well documented from many sections in Asia (cHen et al., 2015a).
The GSSP of the Olenekian Stage has not been defined yet, but two proposals based on the FO of Novispathodus waageni have been put forward (KrYStYn et al., 2007;zHao et al., 2008). Both candidate sections, the Spiti of India and Chaohu in Anhui Province in China, are characterized by presence of E. costatus that has short stratigraphic range. E. costatus has been reported to occur already in the latest Induan in some sections in Asia (zHanG, 1990;iGo, 2009, cHen et al. 2015b. It is worthy to mention here that Nv. waageni has not been collected in the European sections and therefore E. costatus it is currently taken as an important marker around this boundary. The hitherto obtained data from Slovenia and other locations in the Dinarides unabled us to document its entire stratigraphic range and to define its precise stratigraphic position. The preliminary C-isotope data suggests, that the Induan-Olenekian boundary probably lies within the Golob section (cHen et al., 2015a) that means within the range of this taxon. Therefore in the Figure 3 the boundaries of this zone are presented with dashed lines.
The fauna with dominating species P. obliqua and joined by Hadrodontina was assigned to the Smithian P. obliqua Zone and correlated to the P. obliqua Zone in the Dolomites as well as to the Lower Smithian Zone 7 (Parachirognathus-Furnishius Zone) of Sweet et al. (1971). This species has been reported also from South China (WanG & cao, 1981;YanG et al., 1986; and North America (BeYerS & orcHard, 1991).
Remarks: F. gardenae was originally reported from north Italy where it co-occurs with P. obliqua, however, in the upper portion of its stratigraphic range only (StaeScHe, 1964). This species has been later reported from the Dinaric area: Serbia (Budurov & Pantić, 1973;Sudar et al. 2014), Slovenia (Kolar-jurKovšeK, 1990Kolar-jurKovšeK & jurKovšeK, 1995), Croatia (aljinović et al., 2006). A limited geographic distribution of this species suggests it was ecologically restricted. It is possible that its occurrence is confined to the environment of the epeiric ramp conditions (aljinović et al., 2013 a).
In western Serbia, the F. gardenae Zone is distinguished above the E. costatus Zone (Budurov & Pantić, 1974). It is worthwhile to mention that the two taxa have short stratigraphic ranges and according to the presented data, there is an intermediate interval without any evidence of conodont occurrences. Similar distribution revealing occurrence of E. costatus in the older strata and F. gardenae in the younger strata are supported by the situation in the Dolomites (StaeScHe, 1964).

Neospathodus planus Zone
Lower limit: the first occurrence of Neospathodus planus. Upper limit: the first occurrence of N. robustus Koike. Associated taxon: Neospathodus sp.
Remarks: This zone is distinguished based on a new species defined from Slovenia (cHen et al., 2015 a). The specimens of the namebearer of this zone are associated with other neospathodid elements determined as Neospathodus sp.
This zone can be roughly correlated to the lower protion of the P. obliqua Zone. It can be also correlated with the Novispathodus waageni waageni and Discretella discreta Zones which are reported from South China (cHen et al., 2013Yan et al., 2013).

Neospathodus robustus Zone
Lower limit: the first occurrence of N. robustus. upper limit: the last occurrence of N. robustus. Associated taxon: Neospathodus sp.
Remarks: N. robustus was first reported from western Malaysia, and the first entry of this species is documented approximately 10 m higher (ca. 10m) than the LOs of E. costatus and Nv. cf. waageni (KoiKe, 1982). The reports on occurence of N. robustus are very rare.
In the Žiri area the lower N. planus and the succeeding N. robustus Zones are followed by the level with the Platvyllosus elements. Based on obtained data from Slovenia we may conclude that the N. planus and the N. robustus Zones can be correlated to the P. obliqua Zone.
Remarks: This zone is marked by the occurrence of a single species, the zonal namebearer. The P. corniger Zone can be together with the following Pl. regularis Zone roughly correlated with the F. gardenae Zone (see the remarks of the following zone).
Remarks: This zone is marked by the occurrence of a single species, the zonal namebearer. The Pl. regularis has been reported from Serbia for the first time (Budurov & Pantić, 1973) and was assigned to the Ladinian genus Pseudofurnishius (e.g., Budurov & Pantić 1973). However taxonomic revision and new discoveries indicate that it should be assigned to genus Platyvillosus (cHen et al., 2015a, c).
Both Platyvillosus taxa have been collected in two sections in Slovenia, Žiri and Mokrice sections. The older strata in both sections are marked with the fauna of Pl. corniger that are followed by the strata with the fauna of Pl. regularis. Also in the first description of Pl. regularis there is no information about the composition of the fauna that enables us to speculate that the species in the type locality was collected as a monofauna. The absence of any accompaning fauna suggests to stressful conditions controlled by ecollogical factors that renders their comparison difficult.
In both Slovenian sections the Pl. corniger and the Pl. regularis Zones lie below the T. hungaricus Zone, similar as the F. gardenae Zone. Therefore it is reasonable to conclude that the faunas with Platyvillosus and Foliella are contemporaneous in Slovenia.

Triassospathodus hungaricus Zone
Lower limit: the first occurrence of T. hungaricus. Upper limit: the first occurrence of T. symmetricus Orchard.
In the Dinarides T. hungaricus has been just recently collected from Slovenia, as well as from Bosnia and Herzegovina . The species has been also reported from the Sichuan Province, China (tian et al., 1983). Some specimens determined as "N." cf. hungaricus have been collected in Nevada (North America) (lucaS & orcHard, 2007).
Tirolites is widely accepted by stratigraphers as a marker for the Smithian-Spathian boundary (e.g., Kozur, 2003). According to Kozur (2003) the T. hungaricus Zone is presented as the first conodont zone of the Spathian. In the shallow western Tethys, T. hungaricus Zone lies in the lower Spathian, where Icriospathodus collinsoni (Solien) is missing . The present zone can be roughly correlated with the lowermost Spathian Pl. asperatus Zone of the Great Basin, USA (clarK et al., 1979).
In the Mokrice section T. hungaricus occurs as the only species of this zone and it ranges up to the lowermost portion of the following zone characterized by the presence of Neostrachanognathus tahoensis Koike (Kolar-jurKovšeK et al., submitted).
Remarks: T. symmetricus was first reported from Oman and North America and it is accompanied by Ic. collinsoni and T. homeri (moSHer, 1968;orcHard, 1995). In the Slovenian section no accomapanied species were collected. T. symmetricus has also been reported from Italy (Perri, 1986), Greece (dürKooP et al., 1986), North America (moSHer, 1973 and many sections in Asia (see cHen et al., 2015a, b).
This zone can be correlated with the T. symmetricus Zone of North Vietnam and the Ic. collinsoni zone of Jiarong, South China, as both zones lie immediately above the Nv. pingdingshanensis Zone (cHen et al., 2013, 2015bmaeKaWa & KomatSu, 2014).
Remarks: N. robustispinus was first reported from Chaohu, Anhui province (South China), and it occurs in the lower Spathian ammonoid Columbites-Tirolites Zone (zHao et al., 2008). T. homeri (Bender) was first described from Greece (Bender, 1970) and a worldwide distribution of the species is well documented (orcHard, 1995).
In the Slovenian section N. robustispinus is documented higher than the FO of T. symmetricus. The stratigraphic position of this zone can be roughly correlated to T. homeri Zone that is just below the T. triangularis Zone according to (Kozur, 2003). The N. robustispinus -T. homeri Zone in Slovenia probably correlates with the T. homeri Zone in South China (cHen et al., 2013, 2015b).

Triassospathodus triangularis Zone
Lower limit: the FAD of T. triangularis (Bender). Upper limit: the LAD of T. triangularis.
Remarks: T. triangularis was first reported from Greece by Bender (1970) and it has been documented also from the Dolomites (StaeScHe, 1964;Perri & andraGHetti, 1987). The species has widespread distribution and has been extensively reported from many sections of the world (see orcHard, 1995;cHen et al., 2013cHen et al., , 2015b. The marker taxon of the zone was collected also in a few sections south of Ljubljana, however, its entire range has not been well defined. Nevertheles, this zone can be compared to the T. triangularis Zone (Kozur, 2003).

Discussion and conclusions
The PTB interval in Slovenia is characterized by the genera Hindeodus and Isarcicella and the absence of gondolellids is obvious. Therefore, a conodont zonation for shallow facies of the Meishan section in China introduced by WanG (1996) and later refined for the Dolomites in Italy (Perri & FaraBeGoli, 2003) was applied. The Lukač section represents a key section to define the PTB interval strata in Slovenia as well as in the wider Dinarid area (Kolar-jurKovšeK et al., 2011a, 2012. Certain levels of the Lower Triassic succession in Slovenia are marked by shallow water and euryhaline genera. Due to the absence of worldwide biozonal markers, a stratigraphic use of some taxa (i.e. Hadrodontina aequabilis, Ha. anceps, Pachycladina obliqua) was first recognized in the Dolomites, Italy (Perri, 1991) and was later applied also in the Dinarides (jelaSKa et al., 2003). Therefore the use of euryhaline genera is important regional biostratigraphic tool in western Tethys. For some time it was believed that the genus Eurygnathodus Staesche is a junior synonym of Platyvillosus Clark, Sincavage & Stone (e.g., Kozur & moStler, 1973). Therefore there was certain misunderstanding in recognition of some Olenekian genera. In the Treatise of Invertebrate Paleontology (clarK et al., 1981), in the volume of the genus Platyvillosus as a synonym is regarded Eurygnathodus as well as ? Foliella Budurov & Pantić. The three genera have markedly different morphology and they are regarded as separate genera (e.g., orcHard, 2007;cHen et al., 2015a). The genus Platyvillosus was first described from North America and the type species is Pl. asperatus Clark, Sincavage & Stone. The relationship among all known occurrences of Platyvillosus representatives from Europe and North America is not clear.
In Slovenia, Eurygnathodus and Platyvillosus do not co-occur and this is in accordance with the data from Serbia (Budurov & Pantić, 1974). However, their relation is not yet solved. The P 1 element of Platyvillosus is demonstrated by the transitional forms from a neospathodid type ancestor as already suggested by orcHard (2007) and cHen et al. (2015a).
In Slovenia, the genera Foliella and Platyvillosus also do not co-occur and the recovered material does not reveal their relationship. Foliella gardenae has been documented only in Europe, however, the accompanied Pachycladina with an extensive geographical distribution enables worldwide comparison of the fauna.
Platyvillosus taxa have also limited geographic occurrence outside Slovenia. Of the two recognized species, only Pl. regularis has been known to occur in Serbia (Budurov & Pantić, 1973). Their occurrence outside the Dinarides has not yet been reported.
The two neospathodid taxa, Neospathodus planus and N. robustus occur in a level with obvious absence of Novispathodus waageni.
Certain recovered conodont faunas from Slovenia markedly differ from the contemporaneous conodont faunas of North America and Asia. A limited geographic distribution of some genera confined to the European sections suggests they were ecologically restricted and probably adapted to shallow water environments.
Triassospathodus hungaricus has been lately reported from few sections in the Dinarides where it occurs as single conodont species. Outside the area this species has been reported to occur in the Sichuan Province of South China (tian et al., 1983) and moreover, lucaS & orcHard (2007) reported elements morphologically close or identical to "Neospathodus" cf. hungaricus from Nevada.
Representatives of the T. symmetricus-homeritriangularis lineage are well documented and quite common worldwide. are gratefully acknowledged. The investigation was financially supported by the Slovenian Research Agency (programme number P1-0011and project number J1-6665). This is a contribution to the IGCP 572 »Recovery of ecosystems after the Permian-Triassic mass extinction« and IGCP 630 »Permian-Triassic climatic and environmental extremes and biotic response«.